This application relates to a system and method for removing ice at a condenser which is a component of an environmental control system.
Air is typically supplied to an aircraft by conditioned bleed air from the engine. Because this source of air is too hot for the cabin environment, the air flows through an environmental control system that decreases the air temperature by means of exchanging heat through the heat exchangers in a ram air flow circuit. Ram air flow is outside air that passes through the heat exchangers of the environmental control system. The conditioned air then flows through a condenser to condense the moisture out of the air stream to provide a comfortable dry air source to the cabin environment.
The condenser raises challenges with regard to icing, especially on aircraft that do not have the capacity to modulate the amount of ram air flow through the heat exchangers. When the ambient air is especially cold, icing becomes a particular problem since the bleed air from the engine can be cooled to freezing temperatures. Thus, it is known to include an on/off valve that selectively adds hot air from the outlet of a compressor into the inlet of the condenser, and also into the inlet of a second stage turbine.
When the ambient temperature is below a predetermined amount, the valve is commanded to be full open, thus attempting to raise the temperature at the inlet of the condenser to prevent freezing, and to also raise the temperature of the inlet of a second stage turbine to prevent turbine rotor freezing.
However, there is a range of ambient conditions where the temperature is below freezing and aircraft operation provides too much ram air flow. In this condition, the on/off valve does not have sufficient thermal capacity to maintain the condenser inlet temperature above freezing, which can lead to undesirable consequences.